A cerebral aneurysm represents a serious medical condition in which a lesion on a vessel within the crevices of the brain weakens, allowing the vessel wall to expand outward like a balloon. It is estimated that perhaps 2% of the general population live with a cerebral aneurysm, most of which go undetected until the aneurysm suddenly ruptures and causes a subarachnoid hemorrhage in the brain. While the mortality rate from hemorrhage is high (up to 50% within the first two weeks, with many of these occurring immediately), many of the survivors can be spared serious neurological injury or subsequent hemorrhage if treated in a timely manner.
One method of treating cerebral aneurysms involves the use of a plastic or metallic surgical clip that is delivered to the site of the aneurysm to clamp and temporarily or permanently close the vessel or a portion thereof to either prevent further bleeding or prevent rupture, if the aneurysm has been diagnosed in time. One recurrent problem with clipping of the vessels, especially in hard-to-access regions such as within the brain, is that it is difficult to ascertain the presence or absence of blood flow within the vessels before and after the clip has been applied. Of particular concern is the accidental clipping off of non-target branch or vessel. For example, if attempt to treat an aneurysm by clipping either the internal or external carotid arteries which branch from the common carotid supplying blood to the brain, it would be catastrophic, if during application of the clip to cut off flow to one branch, the clip also accidentally cuts off flow to the opposite branch as well.
Ultrasonic Doppler probes have proven to be efficacious in detecting blood flow in a vessel. One such use of Doppler involves monitoring blood flow following vessel anastomosis as a part of organ transplant, reconstructive surgery, and other procedures where small vessels must be reattached and can frequently close off following surgery. Instruments developed for this purpose have involved securing the Doppler transducer head to the vessel, such as with a cuff, then closing the incision with the conductor wires exiting the patient where they are attached to an appropriate ultrasound frequency generator, back-scattering sensor, and control computer. While this has proven to be an effective means of providing longer term monitoring of vessel patency, such a device would not be appropriate when only a single reading is required at multiple locations, such as when clipping an aneurysm, a procedure normally performed using a neuroendoscope. Within the brain, reaching and properly positioning a probe can be problematic due to the restricted space in which to work. Naturally, rigid probes are very limited in their ability to be properly positioned, and flexible probes cannot be controlled sufficiently to be able to assuredly place the transducer at a particular site. Even deflectable catheters are limited in their ability to be adequately maneuvered due to the difficult anatomical constraints typically encountered in attempting to reach a target cerebral vessel, something which can require a series of different bends to achieve the ultimate desired angle of the transducer head.
Therefore, what is needed is an ultrasonic Doppler probe that can be introduced intracranially and manipulated to the desired configuration for traversing the natural spaces, i.e., the ventricles and cisterns, of the brain to measure blood flow at a particular site upon a cerebral vessel to help determine whether an aneurysm has been successfully treated. Furthermore, such as device should be able to be used in combination with standard neuroendoscopes.